Chapter 8 Environmental science

Comments (0)

Transcript of Chapter 8 Environmental science

The Population Bomb Takes a likken and keeps on ticken Opinion Corner What does population mean to you? Lesson 8.3 People and Their Environments The environmental impact of humans depends on the way they live.Poorer societies tend to have smaller ecological footprints than affluent societies, but still strain the environment: Overwhelmed governments can’t supply clean water or adequate sewage treatment.Poverty often leads to land overuse.Deforestation, flooding, disease, and habitat loss can become common, as land is cleared for farming. Environmental Impacts Globally, the average ecological footprint is 2.3 hectares. The average American has an ecological footprint of 9.0 hectares. Lesson 8.3 People and Their Environments Lesson 8.2 Predicting Population Growth Describes the relative numbers of females and malesTypical sex ratio for humans is 1.00 females : 1.06 males. For every 100 females born, 106 males are born.Human activity such as migration can skew sex ratios. Sex Ratio Lesson 8.2 Predicting Population Growth Age structure describes the relative number of people within different age brackets in a population.A population of mostly young people tends to grow. A population of mostly old people tends to shrink.A population with equal numbers of young and old tends to remain stable in size. Age Structure Total fertility rate: Average number of children a female has during her life Replacement fertility rate: The total fertility rate for a nation that would keep its population stable For most nations, a replacement fertility rate of 2.1% would keep population size stable. A greater rate would increase population size; a lesser rate would decrease it. Lesson 8.2 Predicting Population Growth Fertility Rate Some scientists predict that there will be 9 billion people on Earth by 2050, while others maintain that the population will be closer to 10.5 billion. Lesson 8.2 Predicting Population Growth Lesson 8.1 Trends in Human Population Growth • Population size: Number of peoplePopulation density: Number of people living per mi2 (or per km2)Population distribution: How people are distributed within an area Demography: Describing the Human Population Lesson 8.1 Trends in Human Population Growth Populations are likely to grow when infant mortality is low and life expectancy is high.Infant mortality: Number of babies out of 1000 that die during their first year of lifeLife expectancy: Average number of years a person is expected to live Population growth rate describes the change in population’s size during a given period of time. Infant Mortality and Life Expectancy As of 2010, the human population is 6.8 billion (and counting). Lesson 8.1 Trends in Human Population Growth CHAPTER Human Population 8 Did You Know? On average, 1 American consumes as much natural resources as 5 Chinese or 13 Pakistanis. Lesson 8.2 Predicting Population Growth Developing nations: Higher fertility, infant mortality, and death rates Lower life expectancyLow per capita resource use Developed nations: Lower fertility, infant mortality, and death rates Higher life expectancyHigh per capita resource use Social Factors and Population Growth Lesson 8.1 Trends in Human Population Growth Did You Know? To estimate how long it would take any population to double, divide 70 by its growth rate. Growth rate of human population has slowed from 2.1% to about 1.2% since the 1960s.Population growth rates vary by region. Some nations have negative population growth rates, meaning the population is getting smaller.Humans use technology to extend Earth’s carrying capacity for our species. Recent Trends in Human Population Growth Lesson 8.1 Trends in Human Population Growth Did You Know? Basic sanitation was rare even in the medical profession until 1861, when Dr. Ignaz Semmelweis discovered that doctors’ hand washing greatly reduced patient mortality. Advances in agriculture and industry have led to longer lifespans and remarkable population growth. Agriculture: Helped people meet their nutritional needs; increased free time to pursue crafts and tradingIndustry: Improved sanitation, medicine, and food production History of Human Population Growth Solar water pump Negative impacts: Has enabled resource exploitation Has resulted in pollution, biodiversity loss, and climate changes Positive impacts: Enables longer, healthier, more comfortable livesTechnologies such as recycling can help reduce environmental impact.Renewable energy technology can produce cheap, clean energy. Lesson 8.3 People and Their Environments Impacts of Technology Burning of fossil fuels creates a haze of pollution over the eastern coast of China. Did You Know? Globally, 1.4 billion people live on less than $1.25 per day, and another 2.6 billion live on less than $2 per day. Lesson 8.3 People and Their Environments Currently, the richest 20% of the world’s people use 86% of its resources.As developing nations such as China continue to develop, new environmental problems will emerge, as the need for and use of resources increases.Resource availability affects quality of life. The Wealth Gap Demographic transitions are the result of economic growth and social changes. Did You Know? Over the past 50 years, worldwide average life expectancy has increased from 46 to 68 years. Model that explains a population’s change from high birthrates and death rates to low birthrates and death rates Pre-industrial stage: Birthrates and death rates are high.Transitional stage: Birthrates are high but death rates are declining.Industrial stage: Birthrates start to decline; death rates stay low.Post-industrial stage: Both birthrates and death rates fall to low and stable levels. Lesson 8.2 Predicting Population Growth The Demographic Transition